1. Field of the Invention
The present invention generally relates to vehicle propeller shafts and constant velocity joints, and more particularly relates to a cap for use on a constant velocity joint that will release at a predetermined time in a crash event, and with a predetermined load, thus giving the constant velocity joint and the propeller shaft in a motor vehicle a specific crash behavior.
2. Description of Related Art
Propeller shafts (prop shafts) are well known in the art for use in vehicle propulsion systems. The prop shaft may be a multi-piece prop shaft or a solid/single-piece prop shaft depending on the type of drive train system on the vehicle therein. The prop shafts are generally used to transfer torque and rotational forces to the rear axle and rear wheels in all wheel drive, rear wheel drive and four wheel drive vehicles. They also may be used for front axle vehicles and four wheel drive vehicles to deliver the necessary power to the front drive axle. The multi-piece propeller shafts generally are supported by a center bearing and have the necessary support bracketry. This will allow the drive shaft to rotate and transfer the necessary power to the front or rear axle of the automotive vehicle.
In recent years it has also become desirable for the propeller shaft of an automotive vehicle to become a more proactive piece of equipment designed for crash worthiness within the automotive vehicle. This crash worthiness also must be accompanied by prop shafts that are lighter in weight, less expensive and easier to manufacture and install. With regards to crash worthiness of the prop shaft generally, during the crash of a vehicle the body will shorten and deform. Therefore, for safety reasons the propeller shaft should also be able to reduce its length during a crash event at or below a specified load. In the prior art this length reduction is generally achieved by having the prop shaft telescope to obtain a shorter overall length for the prop shaft. The ability of the prop shaft to collapse and telescope within itself will prevent the prop shaft from buckling which may lead to a penetration of the passenger compartment or damaging vehicle components in close proximity to the propeller shaft such as gas tanks, drive axles and other drive train components. Some of the prior art multi-piece propeller shafts were designed to absorb a predetermined amount of energy under both high loads and low loads depending on the characteristics needed from the propeller shaft and the amount of energy needed to be absorbed in the propeller shaft. Many prior art vehicles are generally designed with crumple zones that will allow the vehicle to absorb energy at a predetermined rate during collisions to prevent the transfer of such energy to the vehicle occupants within the passenger compartment. The amount of energy required to collapse the propeller shaft or telescope within itself is the amount of energy absorbed while the telescoping is active and could have an influence on the crumple zone performance of the vehicle during the collision event.
Some of the prior art propeller shafts will deform under certain loading conditions but many of these crash features that are designed into the propeller shaft are often complex and increase the cost of the propeller shaft and constant velocity joint to unrealistic prices. Furthermore, the prior art prop shafts encounter obstacles when they are designed for relatively low collision or collapse forces because a strong robust propeller shaft is required at the same time for everyday use in modem day vehicles. Prior art collapsible propeller shafts tend to absorb energy in a one time manner and once they have collapsed they will no longer perform any energy absorbing characteristics which may be needed to further protect the passenger compartment of the automotive vehicle during the crash event. It should also be noted that some of the prior art collapsing propeller shafts also rely on collapsible constant velocity joints which allow the inner race and other components of the propeller shaft to be expelled through a bore of an outer race to allow the telescoping of the propeller shaft for the absorption of such energy or to prevent high reactive forces from developing in a crash event of an automotive vehicle.
Therefore, there is a need in the art for a collapsible multi-piece propeller shaft including a collapsible constant velocity joint that is capable of being designed to control when and how large the collapsing force profile is during a crash event. There is also a need in the art to produce such a propeller shaft that is easier to install, manufacture, is lighter in weight and will reduce the cost of the propeller shaft and drive train system as a whole. Furthermore, there is a need in the art for a collapsible multi-piece propeller shaft and constant velocity joint that can absorb energy from a collision event of a vehicle at multiple intervals during the crash event. This will help to absorb energy at varying times during the crash event while helping to maintain the structural integrity of the automotive vehicle. The use of such a multi-piece collapsible shaft and constant velocity joint will reduce the cost of making and installing the unit into the automotive vehicle while also reducing any loss of containment of the passenger compartment of a vehicle during a crash event. Therefore, there is also a need in the art for a newly designed constant velocity joint that will allow the crash event to absorb energy at a predetermined rates and absorb predetermined amounts thus effecting greater crash worthiness of the overall vehicle and also not be adversely affected by the weld heat.